FIG. 6 shows a sectional view of a conventional vane pump, which is used in an inspection module for inspecting vapor leakage of fuel from a fuel tank. The vane pump thus employs a brushless motor having no commutating brush.
In FIG. 6, brushless motor 631 includes mounting plate 637 made of metal. Casing 622 of the vane pump is rigidly mounted to plate 637 with bolt 651. Motor housing 632 made of metal plate accommodates rotor 634 and stator 635 of brushless motor 631. Motor shaft 634a is connected to rotor shaft 623a of the vane pump. Motor housing 632 includes cylindrical projection 632a at the center of its top face. Bearing 633 is fixed to an inner wall of projection 632a. 
Mounting plate 637 includes through hole 637a extending along an outer wall of projection 632a, and is fixed to the top face of motor housing 632 by fitting the outer wall of projection 632a into through hole 637a. A structure of the foregoing brushless motor is preferably referred to, e.g. patent document 1.
The conventional brushless motor discussed above; however, has a following problem: When mounting plate 637 is fixed to motor housing 632 at the center of the top face of housing 632 by electrical spot welding, the welding current flows into projection 632a through the contact between projection 632a and the inner wall of through hole 637a, so that bearing 633 can be damaged.
Patent Document 1: Unexamined Japanese Patent Publication No. 2005-98285 (page 5-6, and FIG. 1)